The present invention relates to a charge storage circuit, a voltage stabilizer circuit using the same, and a method for storing charge, and more particularly, to a charge storage circuit using a memory cell of a dynamic semiconductor memory device, a voltage stabilizer circuit using the same, and a method for storing charge.
A supply voltage is a voltage applied to a semiconductor device. A reservoir capacitor is used to prevent the supply voltage from changing by external noise, and a storage capacitor is a capacitor that stabilizes the supply voltage of the semiconductor device by storing charge corresponding to the supply voltage in order to stably apply power to an internal circuit of the semiconductor device. The reservoir capacitor is generally disposed at a peripheral area generally except a memory cell area. In general, the reservoir capacitor is embodied using a MOS capacitor that uses a capacitance of a gate oxide layer of a MOS transistor.
FIG. 1 is a diagram illustrating a MOS capacitor 101 used as a reservoir capacitor according to the related art.
Referring to FIG. 1, the MOS capacitor 101 is embodied using an MOS transistor having a gate for receiving a supply voltage VDD and a source and a drain connected to each other and receiving a ground voltage VSS. An oxide layer of the gate functions as dielectric among the gate, drain, and source and stores charge corresponding to the supply voltage VDD. The MOS capacitor 101 may be realized using a PMOS transistor. In this case, a gate receives a ground voltage VSS and a drain receives a supply voltage VDD.
FIGS. 2A and 2B are diagrams illustrating layouts of a reservoir capacitor with other circuit blocks for describing relations between layout and integration of a semiconductor device. FIG. 2B shows a semiconductor device more highly integrated than that shown in FIG. 2A.
In FIG. 2A, for example, the reservoir capacitor block 203 may have a size of 100 um×100 um (length×width), and the reservoir capacitor block 203 is disposed in an empty space between peripheral circuit blocks 201 and 205. The reservoir capacitor block 203 stabilizes a supply voltage VDD applied to the peripheral circuit blocks 201 and 205. The reservoir capacitor block 203 includes a plurality of reservoir capacitors for minimizing the variation of the supply voltage VDD.
Since the semiconductor device has been densely integrated and reduced in size, the circuit blocks 207 and 211 and a reservoir capacitor block 209 are also reduced in size as shown in FIG. 2B compared to those in FIG. 2A. In FIG. 2B, for example, a reservoir capacitor block 209 has a size of 60 um×60 um (length×width) and includes the smaller number of reservoir capacitors than the reservoir capacitor block 203 of FIG. 2A.
Therefore, the function of the reservoir capacitor block may be deteriorated and the circuit blocks may generate errors due to the variation of the supply voltage as the semiconductor device is reduced in size. If the reservoir capacitors block increases in size for stabilizing a supply voltage, a semiconductor device also increases in size, and Net Die, which is the number of chips per a wafer, is reduced.